A 6-dof device to measure head movements in active vision experiments: geometric modeling and metric accuracy

This work describes a technique for measuring human head movements in 3D space. Rotations and translations of the head are tracked using a light helmet fastened to a multi-joint mechanical structure. This apparatus has been designed to be used in a series of psycho-physiological experiments in the field of active vision, where position and orientation of the head need to be measured in real time with high accuracy, high reliability and minimal interference with subject movements. A geometric model is developed to recover the position information and its parameters are identified through a calibration procedure. The expected accuracy, derived on the basis of the pure geometric model and the sensor resolution, is compared with the real accuracy, obtained by performing repetitive measurements on a calibration fixture. The outcome of the comparison confirms the validity of the proposed solution which turns out to be effective in providing measurement of head position with an overall accuracy of 0.6 mm and sampling frequency above 1 kHz.